dmaengine: shdmac: extend PM methods

In order to make it possible to restore from hibernation not only in Linux but
also in e.g. U-Boot, we have to use sh_dmae_{suspend|resume}() for the {freeze|
thaw|restore}() PM methods. It's handy to achieve this with SIMPLE_DEV_PM_OPS()
macro; since  that macro doesn't do anything when CONFIG_PM_SLEEP  is undefined,
we don't need to #define sh_dmae_{suspend|resume} NULL anymore but we'll have to
enclose sh_dmae_{suspend|resume}() into the new #ifdef...

Based on original patch by Mikhail Ulyanov <mikhail.ulyanov@cogentembedded.com>.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>